The present invention relates to a balance with a balance housing and an operator panel that is attached or attachable to the balance in such a way that it projects forward from the balance housing towards the operator. A balance of this kind is known, e.g., from DE-A-39 39 959.
Operator panels of the kind described in the aforementioned reference are used to a growing extent for managing all of the possible inputs into the balance, using the most advanced kinds of entry means. To the extent that electronic entry means are used, the heat generated by the operator panel may be detrimental to the weighing results, particularly in the case of analytical balances and microbalances. It is to be understood that the invention covers all possible entry means.
One should also consider that balances equipped with these kinds of panels are often used in laboratories for weighing chemical substances, i.e., in an environment where cleanliness is an important requirement. Yet, with permanently attached operator panels of a state of the art as documented, e.g., in EP-A-0 556 473, it is necessary to move the entire balance out of place in order to clean the area underneath, even if the substance to be cleaned away has accumulated only under the operator panel. However, if the balance has been moved, it is often necessary to level it again afterwards, which is time-consuming and labor-intensive.
An improvement in this respect can be found in the aforementioned DE-A-39 39 959 describing an operator panel which can at least be swiveled about a vertical axis of rotation, so that the operator panel moves around the draft shield, but is otherwise firmly connected to the housing. According to the disclosure, the conceptual idea appears to be that the operator panel, which forms an integral unit with the body of the balance, is configured so that its front edge rests on a support surface. However, this supportive contact is not assured when the level of the balance is adjusted. If the level of the balance is raised, a gap or spatial separation occurs below the front edge of the operator panel so that the latter is no longer firmly supported from below. This is a particularly undesirable condition if the operator panel has at least one key that is operated by applying a pressure force perpendicular to the top surface of the panel. The pressure force acting on the key produces a tilting moment that may be detrimental to the accuracy of the weighing result and in any case introduces a bias into the distribution of forces acting on the balance housing.
Thus, as is evident from the preceding discussion, a number of disadvantages can be associated with state-of-the-art balances.
It is therefore the object of the present invention to find a design that eliminates at least a part, but preferably all, of the aforementioned disadvantages that stand in the way of improving the accuracy and operating convenience of a balance.
The invention provides an unexpectedly simple solution of the problem and eliminates the diverse drawbacks of the prior art by proposing a concept according to the features of claim 1.
Not only are the aforementioned deficiencies eliminated but, as an additional advantage, the inventive balance is easier to transport, because it forms a more compact unit when the operator panel is in its rest position. Furthermore, the balance requires less storage space.
The term xe2x80x9cpivoting arrangementxe2x80x9d or xe2x80x9cpivot meansxe2x80x9d as used within this description is meant to imply that the invention is not limited to the operator panel being rotatable about a single geometric axis but rather that the axis itself, too, can tilt and swivel.
In an advantageous embodiment of the invention, the pivot means comprises on one of the pivotally connected parts an axle in the particular shape of a short peg and on the other of the pivotally connected parts a rimmed opening that receives the axle with loose play. On the one hand, the play between the parts is effective in preventing the heat transfer from the operator panel to the balance housing. On the other hand, it also implies that the connection can have horizontal as well as vertical play. In any event, it is preferable to have at least vertical play, so that the connection provides enough mechanical freedom that the balance can more easily be leveled (i.e., height-adjusted) without making a simultaneous height adjustment of the operator panel. With the pivoting arrangement allowing the operator panel to rotate vertically, the latter can adjust itself to a possibly sloping support surface, e.g., a tabletop.
If the rimmed opening is about U-shaped so that the axle peg can slide out through the open side of the U, this will make it easier to remove the operator panel, e.g., in order to replace it with a different type of panel, or for repair and maintenance. If desired, the operator panel may even be detached when the balance is stored away.
Particularly in laboratories where chemicals can get spilled, it is important that an electrical connection, as it is generally provided for the operator panel, is still protected from the possibly destructive effects of spilled chemicals, even with the pivotal connection between the operator panel and the balance housing. The protection from spilled chemicals is advantageously accomplished by providing a connecting cable that exits from the balance housing in the vicinity of the pivot means, because this allows the connection to be kept relatively short so that the cable does not need to rest on the supporting surface.
In a preferred embodiment, the cable is at least approximately coaxial to the pivot axle and runs through the latter so that the cable is subjected to as little bending as possible.
As another measure to facilitate replacing or removing the operator panel from the balance housing, the cable leaves the balance housing through a cover lid, particularly a plate-shaped cover, that is removable from the balance housing, being connected to the latter through a releasable fastening element.
Further details of the invention are presented in the following description of a particularly preferred embodiment as shown schematically in the drawing.